Capture fail in Lenovo Thinkpad X220 (Conexant CX20590)

Hello, 

with my laptop Lenovo X220 Thinkpad I can listen sound but I can not
capture any sound. 

If I plug an external microphone in combo connector, sound card detects
that I have plugged microphone but I don't capture anything. 

I look in pavucontrol, alsamixer, arecord, aplay output, but I can not
find anything. 

# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: CX20590 Analog [CX20590 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0 

Any help is welcome.